[media] cx231xx: fix compiler warning

Fix this compiler warning by allocating a structure to read the eeprom instead
of doing it on the stack and worse: the eeprom array is static, so that can
cause problems if there are multiple cx231xx instances.

cx231xx-cards.c: In function 'cx231xx_card_setup':
cx231xx-cards.c:1110:1: warning: the frame size of 2064 bytes is larger than 2048 bytes [-Wframe-larger-than=]
 }
 ^

I did consider removing the code altogether since the result is actually
not used at the moment, but I decided against it since it is used in other
drivers and someone might want to start using it in this driver as well. And
then it is useful that the code is already there.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>